Electron space discharge device



Aug. 23, 1955 H. R. JACOBUS, JR 2,716,200

ELECTRON SPACE DISCHARGE DEVICES Filed Nov. 20, 1951 2 Sheets-Sheet l E-4- JNVENTOR.

Aug 23, 1955 H. R. JAcoBus, .1R 2,716,200

ELECTRON SPACE DISCHARGE DEVICES Filed NOV. 20, 1951 2 Sheets-Sheet 2 .lz-E13.

INVENTOR.

United States Patent O ELECTRN SPACE DSCHARGE DEVC S Herbert R.. Jacobus, Jr., White Plains, N. Y., assigner to Sonotone Corporation, Elmsford, N. Y., a corporation of New York Application November 2), 1951, Serial No. 257,323

1 Claim. (Cl. 313 261) This invention relates to electron space discharge devices in which an electrode assembly comprising at least an anode and a cathode are enclosed in a hermetically sealed envelope, and more particularly to such electron discharge devices which are known commercially as subminiature electron tubes, although some of the features of the invention are applicable to electron space discharge tubes other than sub-miniature tubes.

Among the objects of the invention are sub-miniature tubes embodying novel features which make it possible to manufacture on a production basis an extremely ruggedized tube capable of withstanding great mechanical shock, such as undergone in a proximity fuse, without substantially impairing the electrical characteristics of such tube.

The foregoing and other objects of the invention will be best understood from the following description of exemplilications thereof, reference being had to the accompanying drawings wherein:

Fig. l is a vertical cross-sectional View of one form of a multi-electrode sub-miniature tube exemplifying the invention;

Fig. 2 is a vertical cross-sectional side View of the same tube in a direction transverse to Fig. l;

Pigs. 3 and 4 are detailed cross-sectional views of an upper and lower portion, respectively, of the tube showing the wedge action with which the insulating spacer holds the cathode;

Fig. 5 is a cross-sectional view along line 5 5 of Fig. l;

Fig. 6 is a cross-sectional view along line 6 6 of Fig. l;

Fig. 7 is a cross-sectional view along line 7 7 of Fig. l;

Fig. 8 is a plan view of the mica spacer;

Fig. S-A is a plan view of' the center portion of an insulating spacer which exemplifies another form of the invention;

Figs. 9 and 12 are front and rear elevational views of an anode of the tube exemplifying one form of the invention;

Figs. l0 and ll are side elevational and plan views, respectively, of the anode shown in Fig. 9,

Fig. 13 is a cross-sectional view of an anode or" the tube exemplifying another form of the invention.

Although the principles of the invention are applicable to other types of sub-miniature tubes, and some aspects of the invention are of a broader scope, their application will be described in connection with a pentode-type tube shown in Figs. 1 through 7, which has a very wide use as a voltage gain and power amplifier.

Referring to Figs. l to 7, the tube shown comprises an evacuated, generally elongated tubular envelope 11 of vitreous material such as glass, which encloses an electrode assembly generally designated 10. The electrode assembly 10 comprises a plurality of electrodes which are connected to a plurality of leads 12, 13, 14, 15, 16, 17 and 18 hermetically sealed through an electrically ice insulating terminal end wall portion 19 of the envelope 11 to provide external circuit connections to the electrodes. The terminal end wall portion 19 is made in the form of a wafer-like stern ot' vitreous material sealed around portions of the lead conductors 12 to 18 which are arranged thereon in a circular row. The wafer-like lead stern 19 extends in a direction transverse to the envelope 11 and is fused to its lower end border.

The electrode assembly 10 comprises an indirectly heated cathode 21, a control grid 22, a screen grid 23, a suppressor grid 24 and an anode 25, all extending longitudinally generally parallel to a common axis of the electrode assembly 10. In the specific tube shown, the cathode 21 comprises a thin tubular open-ended sleeve of a ductile metal, such as nickel, and provided with an oxide coating which emits electrons when heated to an elevated temperature. The tubular cathode 21 is heated by a thin filament 29, of a refractory metal such as tungsten, which is shown as V-shaped and is positioned inside the cathode sleeve 21. The two terminal ends of the heating filament 2G are provided with mounting portions in the forni of metal tabs 28 to which the ends of the filament are secured as by welding, and which are in turn secured to the external lead conductors 12, 13. The heating filament 2) is coated with an electrically insulating coating which insulates the filament 20 from the cathode sleeve 21. External circuit connection to the cathode sleeve 21 is made by electrode lead 1S which is electrically connected thereto through a metal link 27.

The three grids 22, 23, 24 are made of very fine refractory metal wire, for instance, tungsten wire. The inner control grid 22 is wound as a helix on and secured to two inner grid posts 29. The intermediate screen grid 23 is similarly wound and supported on two intermediate grid posts 3i). The outer suppressor grid 24 is also similarly wound and supported on two outer grid posts 31. The grid posts of such sub-miniature tubes are usually formed of thin wires.

Electrode leads 16 and 17 are directly connected to a grid post of the screen and suppressor grid 23, 24, respectively, and provide external circuit connections to such grids. External circuit connection to the control grid 22 is made by electrode lead 14 which is connected to one end of a metal connecting link 32, the other end of which is connected to the control grid post 29.

The grid posts as well as the indirectly heated cathode 21 and the anode 25 are held in their operative position by two similar generally flat sheet-like insulating spacer elements 33, 34 of a material having a high dielectric constant, such as mica. The two spacers 33, 34 are provided with apertures or openings engaged by junction or supporting ends of the grid posts and of the other electrodes which are joined by two spacers 33, 34 into a self-supporting electrode assembly.

There are many applications of sub-miniature tubes, as in proximity fuses, in which it has to retain its essential electronic operating properties and in which it has in addition, to exhibit the critical characteristic of high resistance to mechanical shock. When a shell containing a proximity fuse is propelled from a gun with tremendous acceleration, all of the elements comprising the proximity fuse undergo a tremendous initial shock. This applies also to the electron space charge devices of such proximity fuse which contain very delicate elements which have to be maintained in highly critical relative spacing.

For satisfactory operation of such discharge tubes, it is essential that the cathode occupy its properly spaced operative position within the electrode assembly 10, and be retained therein by a rugged structural system so as to withstand any and all distortive stresses to which it is subjected, for instance, when the electrode assemby is accelerated at high rate, as in a proximity fuse. Because of the close electrode spacing, the problem of properly retaining the cathode in its operative position is critical, particularly if such tubes are to be manufactured at low cost on a mass production basis.

One phase of the invention involves a novel rugged interconnection of the cathode to the associated elements of the electrode assembly, which permits their assembly by relatively unskilled labor on a production basis.

According to the invention, such rugged cathode cons nection is obtained by providing the spacer opening 37, which retains the cathode 21 in its operative position by engaging a junction portion thereof with one or more stiff tongue projections 36 extending from the border of such spacer opening 37 in the insulating spacers 33, 34 which is arranged to hold the cathode junction portion firmly wedged therein.

In the specific form shown (Figs. 3 to 8), each spacer 33, 34 consists of two substantially identical insulating sheet elements 41, 42 which are cemented together to form the completed spacer, each sheet element having two oppositely facing stiff tongue projections 36 extending from the border of the spacer opening 37. The space separating the two facing tongue projections 36 of the upper sheet element 41 of the upper spacer 33, and of the lower sheet element 41 of the lower spacer 34 is slightly smaller than the width of the cathode sleeve 21. On the other hand, the space separating the two facing tongue projections 36 of the bottom strip -42 of the upper spacer 33, and of the top strip 42 of the lower spacer 34 is equal to the width of the cathode sleeve 21. The two opposite junction ends of the cathode sleeve 21 are each provided with a small flange 45 having a generally larger diameter than the width of the spacer opening 37 which holds the cathode 21 in its proper operative position.

Upon assembly of the cathode-spacer unit, the cathode sleeve 21 is pushed into engagement with the space opening 37 of the xedly held upper insulating spacer 33 until the flange 45 on the upper junction portion of the cathode sleeve 21 engages the inner surface of the insulating spacer 33. Referring to Fig. 3, as the space between the two facing tongue projections 36 of the bottom insulating strip 42 is equal to the width of the cathode sleeve 21, the cathode sleeve 21 will t smoothly through the bottom insulating strip 42. However, since the space between the two facing stiff tongue projections 36 of the top insulating strip 41 is slightly smaller than the width of the cathode sleeve 21, the two tongue projections 36 will be slightly bent in an outward direction rmly wedging against the surface of the cathode sleeve 21 and providing an extremely rigid connection therebetween which will absorb an enormous amount of mechanical shock without lateral displacement of the cathode sleeve 21 relatively to the insulating spacer 33.

Similar results follow when the lower spacer 34 is pushed into engagement with the free end of the cathode sleeve 21 until the inner surface of the lower spacer 34 engages the flange 45 on the lower junction portion of the cathode sleeve 21. Referring to Fig. 4, the two sti tongue projections 36 of the bottom strip 41 of the lower insulating spacer 34 will be slightly bent in a downward direction firmly wedging against the surface of the lower portion of the cathode sleeve 21 and rigidly securing it to the lower insulating spacer 34. The two flanges 45 engaging, respectively, inner facing surface portions of the insulating spacers 33, 34 prevent any movement of the cathode sleeve 21 in an axial direction.

This phase of the invention provides a simple but extremely accurate method for rapidly assembling the cathode sleeve 21 in its proper operative position within openings 37 in the insulating spacers 33, 34 using unskilled labor. lt also provides an extremely rigid connection between the cathode sleeve 21 and the insulating A spacers 33, 34 thereby preventing lateral movement there- Y edges of the anode 25 has two spaced ears 50, interlock between with its consequent impairment of the electrical characteristics of the electron space discharge device.

The stiif tongue projections 36 of the insulating spacers 33, 34 have sufhcient resiliency so that they may be bent relatively to the insulating spacers 33, 34 without fracturing when the cathode sleeve 21 is inserted into the spacer opening 37. The two bent stiff tongue projections 36 will firmly wedge the cathode sleeve 21 therebetween and prevent lateral movement of Such cathode sleeve 21 relatively to the insulating spacers 33, 34.

Fig. S-A illustrates another form of insulating spacer 33 for holding the cathode sleeve 21 exemplifying another form of the invention. In the specific form shown, four stiff tongue projections 36-1, 36-2 will be engaged by the cathode sleeve 21 firmly wedging against the surface thereof so as to rigidly secure it to the insulating spacer 33. Two stiff tongue projections 36-1 correspond to the stiff tongue projections 36 shown in Fig. 8. The other two tongues 362, which lie along a line substantially perpendicular to the first tongues 36-1, engage facing surface portions of the cathode sleeve 21 yin a manner similar to the one in which the rst tongue 36-1 engage the cathode sleeve 21. The distance between the tongue 36--2 is slightly smaller than the width of the cathode sleeve 21 so that they are slightly ilexed by engagement therewith thereby wedging and tightly holding the cathode sleeve 21 in its proper position.

As shown in Figs. 1 through 7, the peripheral edges of the insulating spacers 33, 34 are shaped to engage inner spaced surface portions of the envelope 11 and serve to' maintain the electrode assembly 10 in its properly spaced and aligned position within the envelope 11.

A sheet metal anode 25 surrounds the grid structures 22 to 24 and is arranged to receive the electrons emittedv by the cathode sleeve 21 under the control of the control grid 22, in a manner well known in the art.

Another phase of the invention consists of providing a substantial increase in the rigidity of the anode 25 by pro-i viding one or more rigid supporting rods 57 extending adjacent the surface of the anode 25 joined to spaced surface projecting cut-out portions or ribs 55, 56 of the anode 25 and having junction ends confined in openings 58 in the insulating spacers 33, 34. l

continuous sheet structure of thin refractory metal, vsuchas nickel. Each of the opposite generally oval boundary ingly engaging and intertting with two spaced `recesses 51 in the two opposite spacers 33, 34, so as to secure the two spacers 33, 34 to the upper and lower ends, respectively, of the anode 25 and join them into a self-supporting unit.

ln the specific form shown, to provide increased rigidity between the anode 25 and the spacers 33, 34, one surface of theanode 25 is provided with two cut-out portions or. tongues or ribs 55 which project outwardly in a verticali.

plane to the surface of the anode 25. The oppositelyfacing surface of the anode 25 has one similar cut out portion or tongue or rib 56 generally positioned centrally between the two oppositely facingtongues 55 on the opposite surface of the anode 25. Each of the projecting tongues or cut-out portions 55, 56 lie in a plane generally parallel to the common axis of the tube. Three spaced rigid supporting rods 57 extending generally parallel to the commonA axis of the tube and adjacent to the outer surface of theianode 25 abut the junction, respectively, of each of the? projecting tongues 55, 56 with the surface of the anode 25 and are secured, as by welding, to the adjacent tonguesl The cut out portions or tongue projections 55, 56 are obtained by partially severing spaced surface portions ofi the anode 25 between opposite end regions thereof and displacing such partially severed portions in an outward direction so that they extend at a generally right angle to the surface of the anode 25.

Upper junction portions of the supporting rods 57 engage openings 58 in the upper insulating spacer 33 thereby securing such supporting rods 57 thereto. The portion of the supporting rods 57 extending above the upper insulating spacer 33 is provided with a small welded tab 59 which engages the outwardly facing surface of the upper insulating spacer 33 thereby preventing axial movement of such spacer 33 relative to the supporting rods 57.

The lower junction portions of the supporting rods 57 pass through openings 58 in the lower insulating spacer 34 and are hermetically sealed through the end wall portion 19 of the tube.

Thus, substantial rigidity of the anode structure 25 is obtained by atlixing spaced projecting surface portions 55, 56 thereof to a plurality of rigid supporting rods 57 having one junction end, respectively, conned in an opening 58 in the upper insulating spacer 33 and having the opposite junction end secured through the lower insulating spacer 34 and sealed through the rigid end wall portion 19 of the tube, which is a part of the rigid envelope 11. Such sealed through junction portions of the rigid supporting rods 57 also provide external circuit connections to the anode 25.

The opposite boundary edges of the anode 25 seat along their entire periphery, respectively, against the inner surfaces of each of the insulating spacers 33, 34 to provide a rigid unitary structure. To permit the escape of gases formed within the electrode assembly during the bombing and evacuation of the completed tube, the opposite surfaces of the anode 25 not containing the projecting tongues 55, 56 are provided with substantially large openings 60.

Fig. 13 shows another form of anode construction exemplifying this phase of the invention which is illustrated by a diode-type tube, in lieu of the pentode-type tube shown in Figs. 1 through l2.

Referring to Fig. 13, in the specific form shown, the electrode assembly comprises an indirectly heated cathode 21 surrounded by an anode 69. The indirectly heated cathode 21 consists of a thin tubular metal structure having an oxide coating which emits electrons when heated to an elevated temperature in a manner similar to that shown in Figs. 1 to 7. The indirectly heated cathode 2l encloses a heating filament likewise similar to the heating filament shown in Figs. l to 7.

A sheet metal anode 69, of a generally oval shape, surrounds the cathode 21 and is arranged to receive the electrons emitted by the cathode 21 in a manner well known in the art.

The anode 69 is supported and further rigidiiied by three rigid supporting rods 71, 72 in a manner similar to that shown in Figs. 1 to 12. In this modified form, two spaced projecting surface portions 70 are formed in the` oppositely facing anode surfaces at one end of the generally rectangularly-shaped anode 69, and two rigid supporting rods 71 are aixed, respectively, thereto.

A third rigid supporting rod 72 is ailixed between inner surface axially extending junction portions 73 at the othc;Y end of the generally rectangularly-shaped anode 69.

The three rigid supporting rods 71, 72 are confined at opposite junction ends in the upper and lower insulating spacers 33, 34 in a manner similar to that shown in Figs. l to 7. The bottom junction portion of each rigid supporting rod 71, 72 is further secured by being hermetically sealed in the rigid end wall portion 19 of the tube likewise in a manner similar to that shown in Figs. 1 to 7.

Thus, further rigidness of the anode 69 is obtained by aixing spaced projecting portions thereof to a plurality of rigid supporting rods 71, 72 which are conned in openings in the insulating spacers 33, 34 and are further secured by being sealed through the end wall portion 19 of the tube.

As shown in Figs. l, 2, 3, and 5, the portions of the suppressor grid rods 24 extending above the upper insulating spacer 33 has secured thereto a getter support in the form of two metal strips 65. The two getter support strips 65 have formed therein a pocket 66 with an opening facing the adjacent side wall portion of the envelope 11 and a body of getter material 67 held axed within the pocket. The two getter support strips 65 also act as barriers to confine the evaporated vapors of the getter material 67 to the region of the envelope facing the outer surface of the getter support 65 and substantially preventing getter vapor from materially reducing the surface leakage resistance of the upper insulating spacer 33 to leakage current.

It will be apparent to those skilled in the art that the novel principles of the invention thereof will suggest various other modifications and applications of the same. it is accordingly desired that in construing the breadth of the appended claim they shall not be limited to the specific exempliiications of the invention described above.

I claim:

In an electron space discharge device, an electrode assembly including an anode, a cathode and at least one further electrode interposed between said anode and said cathode, all of said electrodes extending generally parallel to each other and each having opposite elongated junction portions, two opposite generally at resilient spacing structures of insulating material and each having junction openings engaging the opposite junction portions of each of said electrodes passing through said openings for holding said electrodes insulated from each other in laterally spaced operative positions, each of said spacing structures comprising a at inner plate member and a flat outer plate member positioned in overlapping contact engagement with each other, plate portions of each respective outer plate member which border the cathode junction openings through which the respective cathode junction portion passes constituting at least three stil restraining tongues which are angularly displaced from each other by at most said three tongues being elastcally displaced from their original position in the respective plate and being held by their elastic restoring forces in wedging restraining engagement with at least three similarly angularly displaced surface portions of the cathode junction portion passing through the respective cathode junction opening, opposite junction portions of each of the other electrodes of said assembly being surrounded on all sides and in engagement with the edges of the junction openings of the respective outer plate member through which they pass.

References Cited in the tile of this patent UNITED STATES PATENTS 2,048,257 Glauber July 21, 1936 2,082,851 Smith June 8, 1937 2,150,323 Green Mar. 14, 1939 2,494,853 Alma Jan. 17, 1950 2,617,069 Zorgman Nov. 4, 1952 

